Cigarette filter tow refers to a large strand of crimped, continuous, manufactured filaments, e.g. cellulose acetate filaments, that is collected in a loose, rope-like form and then compacted into bales for use by cigarette filter manufacturers. In processing the tow to form cigarette filters, the compacted and baled tow first is opened, or "bloomed" in a tow opening device. The tow is opened to increase its bulk. This bulking is accomplished by deregistering or misaligning the crimps or folds in the tow and is important to provide more fiber surface area for contact with cigarette smoke so that less fiber weight per filter tip can be used.
The opened tow is transferred to rodmaking machinery. The rodmaker compresses the tow into a continuous rod, wraps the rod in plug wrap paper to which an adhesive previously has been applied, and cuts the rod to form cigarette filter tips. These tips are suitable for use in the cigarette forming machinery.
Explemary methods and apparatus for blooming cigarette filter tow, transferring the bloomed tow to rodmaking machinery, and forming cigarette filter rods therefrom are discussed in U.S. Pat. Nos. 3,050,430; 3,016,945; 3,099,594; 3,173,188; and 4,522,616; and German Patent Application No. 0 269 915.
FIG. 1, labeled prior art, herein shows a typical, commercially available, rodmaking apparatus, the Hauni KDF-2 brand rodmaker. Rodmaking apparatus generally includes a section referred to as the "garniture," in which the filter rod is formed. The tow is received into the garniture from the tow opener through the relatively narrow opening, or intake, of a tapering body called the "garniture tongue." It is the function of the garniture tongue to compress the tow into a cylinder of the appropriate size for forming filter rods so that the tow can be wrapped by the plug wrap paper. The tow and plug wrap paper are conveyed through the tongue by an endless belt, the "garniture tape," from which the tow and plug wrap are released when the rod is formed, wrapped, and sealed.
The cigarette manufacturer typically desires a cigarette filter that, among other things, has a particular firmness, resistance to draw, and smoke filtration efficiency, all at the lowest possible cost and greatest efficiency of production. If the manufacturer consistently and at high processing speeds can reduce the weight of tow necessary to achieve a desirable firmness, smoke filtration efficiency, and resistance to draw, or pressure drop across the rod, then a cost savings typically is realized. Tow yield is maximized.
A "transport jet" and funnel, for example see FIG. 3 of U.S. Pat. No. 4,522,616, are used at higher processing speeds to increase efficiency and reduce costs of production. The jet and funnel introduce the opened tow from the tow opening apparatus into the relatively narrow opening of the garniture tongue intake. The transport jet is a pneumatic device that uses a compressed gas, typically air, in a venturi nozzle to assist in delivery of the opened tow into the garniture tongue. The funnel assists in precluding tow filaments from travelling outside the garniture tongue and in dissipating the compressed air exiting the jet, thereby to reduce disruption of the tow in the garniture by the transport gas. FIG. 2 herein shows a longitudinal section through such an arrangement, which is typical of the prior art.
Air holes for dissipating transport gas may be provided on the garniture tongue intake, the annular wall of the funnel to the garniture, or in the venturi nozzle of the transport jet on the tow opening device. Transport gas is also blown back in the direction of the transport jet, opposite the direction of travel of the tow, by the annular wall of the funnel.
European Patent Office Application No. 0 269 915 describes an apparatus that uses a transport jet and garniture funnel for forwarding a cigarette filter tow into the garniture tongue intake. In this device, the garniture intake is also supplied with compressed air through apertures in the intake wall. The compressed air enters the flow path of the tow in the direction of tow travel and at an angle less than 90.degree. with respect to the axis of tow travel. A series of apertures is provided along the tongue so that the compressed air can be radially dissipated. Air is supplied to the garniture intake at a pressure of approximately 5 bar with air consumption of approximately 8 m.sup.3 per hour.
The use of transport jets in combination with funnels typically has been acceptable. However, tow tends to accumulate in the funnel after exiting the transport jet, thereby impeding delivery of the tow to the garniture. It would be desirable to eliminate the funnel and to thereby substantially eliminate accumulation of tow in the region between the transport jet and garniture tongue so as to provide substantially unimpeded transport of opened tow from the tow opening apparatus to the garniture tongue.